This invention relates generally to retractable locking safety belts and more specifically to an improved lockup control for a pawl and ratchet type seat belt retractor lockup mechanism.
Seat belt mechanisms tend to fall within three distinct categories. First is the category of "web sensitive" retractors wherein the belt is normally in an unlocked but retractively biased condition whereby sudden protractive movement of the belt results in lockup preventing further protraction thereby restraining the passenger. The second type is generally referred to as "vehicle sensitive" in which the normally unlocked belt is locked up in response to sudden vehicle acceleration or deceleration to prevent further protraction of the belt thereby restraining the passenger. In this type of retractor the vehicle accelerations and decelerations are sensed by a pendulum or other type of inertial mass. The third category of retractors, which includes the present invention, are normally-locked in that the retractor mechanism allows belt protraction sufficient for the belt to extend across the torso of the passenger and be buckled, subsequent retraction in response to a retractor spool biasing spring to allow the belt to become snugly fitted to the torso of the passenger, and then locked against further protraction thereby providing continuous restraint to the passenger until such time as the belt is unbuckled.
The prior art in this third category consists of mechanisms that accomplish this initial protraction, retraction and locking function. Until the present invention this has been accomplished by the use of two separate means. The first means senses the direction of rotation of the seat belt spool, and operates to allow unrestricted retractive rotation of the spool by inhibiting locking engagement of the pawl and ratchet assembly. This first means does not inhibit locking engagement during protractive rotation of the spool thus allowing passenger restraining lock-up. Since this first means acts as a one-way gate to rotative motion of the spool, a second, independent means has been provided to augment the operation of said first means and allow protractive rotation to be initiated whenever the belt is in a fully retracted condition. Together, these two means permit a full cycle of belt positioning.
U.S. Pat. No. 3,174,704 entitled "RESTRAINT APPARATUS", issued to E. H. Replogle on Mar. 23, 1965 and assigned to the common assignee of this invention teaches the use of a ratchet assembly to accomplish lockup. In this assembly, the seat belt retractor includes a retracting spool rotatably journalled in the retractor frame and which windably retracts the seat belt. Fixedly attached to and axially displaced from said spool is a ratchet disc having engageable teeth. Also carried by the frame is a pawl having a limited rotary motion from an unlocked to a locked position whereby the locked position is such that the pawl engages the ratchet teeth of the retractor spool, thereby preventing protractive rotation of said spool. This pawl and ratchet assembly is referred to therein as deactivatable stop means.
A deactivator means is provided in Replogle for inhibiting lockup by lifting the pawl out of engagement with the ratchet disc to the unlocked position in response to retractive rotation of the spool. This construction permits retractive rotation of the spool without either the drag or noise associated with the pawl ratcheting over the teeth of the ratchet disc. The sensing of the direction of spool rotation is accomplished by a combination of friction drum and a deactivator finger portion of the deactivator means. The deactivator finger is rotatable between limits to attain a first, activated position and a second, deactivated position by frictional contact with the friction drum which is integral with the retractor spool. Upon a change in direction of rotation of said spool, said finger tends to move in a coupled fashion with said spool from one of said positions until it acquires the second of said positions. The finger retains the latter position throughout further rotation until such time as the direction of rotation is reversed.
A second deactivator means is provided, known as a sensor means, for sensing the amount of belt retraction by sensing the thickness of the belt winding about the spool. Upon reaching the fully retracted condition, the sensor senses the increased thickness of the belt windings about the spool, lifts the pawl out of engagement with the spool, and thereby allows an initial protractive rotation of the spool from the fully retracted condition.
In operation from the initial fully retracted condition, the Replogle apparatus allows the seat belt to be protracted sufficient to be buckled up, retracted to acquire the proper fit about the torso of the passenger, and then locked against further protraction. The apparatus continues to be locked against further protraction until such time as the belt is unbuckled and again fully retracted onto the retractor spool.
A subsequent patent entitled "SELF-RETRACTING WEBBING ROLLER FOR SAFETY BELTS", U.S. Pat. No. 3,412,952 issued to G. Wohlert et al. on Nov. 26, 1968 and assigned to the common assignee of this application again uses a pawl and ratchet assembly to accomplish lockup against further protraction of the seat belt. Wohlert teaches the use of a control disc adjacent to and in frictional contact with said ratchet disc and having a limited rotation from lockup permitted to lockup inhibited positions. The positions are defined by control disc rotation between stops relative to said ratchet disc whereby portions of the control disc selectively occlude the ratchet teeth preventing the pawl from engaging the ratchet disc. Similar to the deactivator finger and friction drum assembly of the Replogle patent, the Wohlert control disc operates by frictional contact with the spool to produce movement in a coordinated fashion relative to the ratchet disc whenever said spool changes rotative direction.
An independent sensor means similar to that of Replogle is also provided by Wohlert for sensing the amount of seat belt retraction and inhibiting locking engagement of the pawl with the ratchet disc whenever the windings of the belt about said spool exceed a predetermined thickness associated with the substantially fully retracted condition. Accordingly, operation of the Wohlert apparatus is similar to the operation of the Replogle apparatus.
The "LOCKING SEAT BELT RETRACTOR" patent issued to Robert C. Fisher, U.S. Pat. No. 3,667,698 issued June 6, 1972, teaches the use of a turn counting mechanism as an independent means in place of the sensor means for sensing belt winding thickness of the Wohlert and Replogle patents. The Fisher patent teaches the use of a direct drive gear assembly to locate a cam surface in such manner as to inhibit lockup of a pawl with a spool associated ratchet disk during a predetermined range of spool positions corresponding with a specified number of spool rotations from the fully retracted condition. Again, a control disc arrangement similar to that disclosed in Wohlert is disclosed for inhibiting motion of the pawl into locking engagement with the ratchet disc during retractive rotation of said disc by the coordinated rotation of the control disc due to frictional contact with the retractor frame between limits of rotation in the form of stops.
In all of these prior devices, multiple separate, distinct, and independent means were required to control pawl motion from the unlocked to the locked position in response to first, retractive rotation of the retractor spool when the associated safety belt has been protracted to a position of use, and second, protractive rotation of the retractor spool when said protractive rotation is initiated from a substantially fully retracted condition. To my knowledge no means was known prior to the present invention for accomplishing both types of control with a single pawl control means. Accordingly, it is therefore an object of the present invention to provide and disclose a single pawl control means responsive to both the direction of rotation of the spool, when the safety belt has been protracted to a position of use and to the amount of spool rotation during the protractive rotation of said spool from and to a substantially fully belt-retracted condition.
It is another object of the present invention to disclose and provide a unitary pawl control mechanism for determining when the belt is in said substantially fully retracted condition and for sensing the direction of spool rotation when the safety belt has been protracted to a position of use to provide an automatic lockup of an associated safety belt retractor mechanism.
It is a further object of the present invention to disclose and provide a pawl control means as in the foregoing object and that has an economy of moving parts thereby reducing the cost of manufacture.
It is a still further object of the present invention to disclose and provide a pawl control means for an automatic locking retractor with spool position and direction of rotation sensing means that is of simple and reliable construction and operation, thereby minimizing possible modes of failure and the costs of repairs.